Tuesday, 11 November 2014

Hidden Behind the Load Balancer

Of course you would have been working hard to place your Exchange CASArray’s and Webmail services behind a decent load balancer with decent health
checks. (BTW you are only as good as your health checks!!)

Never the less, even in the best designed solutions there is always cracks, things that are missed or worse when things kinda fail but kinda still work. Of course for users they speak first to colleagues, neighbours, Twitter, Facebook and then finally the IT service desk.

It’s always helpful to confirm
which back end client access server the user is currently connecting to, adding
this information into an existing ticket will assist confirming if you are
indeed have an issue with a single server in your farm.

Of course this is helpful with
some aspects such as confirming which type of connection is being used or the number of failed connection being made are important but this fails to confirm which client access server the user is actually hitting behind the load balancer.

OWA is a little better. We have
to love the “about” button which cuts straight to the chase and provides details
for which Exchange Client Access server is in use and even what roles are used
by this server.

Better still is the requirement
to all the connections in one go. To do this you can use the following:

I was disappointed to hear last
year at TechEd that this CMDLet is no longer going to be supported and used in
Exchange 2013. Microsoft have been asking for business cases for
some time but clearly it lost. So what can we do from here?

Well moving forward you can always trace the IIS and RPC logs for user connections. Here's one I created a while back. It's a simple script to track the users and can be used to find anything in the logs such as throttled users.

$PathCAS001="\\cas001\C$\inetpub\logs\LogFiles\W3SVC1"

$PathCAS002="\\cas002\C$\inetpub\logs\LogFiles\W3SVC1"

$Getdays=1

$outputpath="C:\Scripts\IISfind\Output"

$Date=Get-Date

$DateShort= (Get-Date).ToString('yyyyMMdd')

$SearchValue=Read-Host"Please enter a value to seach the IISLogs (eg.
UserID):"

Another helpful tool you could also use is Log Parser (http://technet.microsoft.com/en-au/scriptcenter/dd919274.aspx) which assists tracing these logs.

For RPC searches just change the source directory to the
RPC Log directory and rerun the script across all your Client Access Servers.

I spoke to Scott Schnoll a
while back about it here is my case for Get-LogonStatistics.

Subject: Case Study: Get-LogonStatistics

Hi Scott,

We had a quick chat on Friday and
I said I would forward you a case we encountered which required the use of the
get-logonstatistics CMDlet.

User Issue: Users were experiencing bad outlook performance to a
single datacentre with numerous connects and disconnects throughout a single
day.

Core Issue: Due to recent Junos firewall upgrade in the core we found
that this firewall had enabled ALG for RPC traffic enabled which was dropping
active RPC connections to this datacentre. This would result in outlook not
responding and making a new connection to the CAS server. These new connections
in turn created the problem that users were starting to breach their throttling
limits. MS Support recommended increasing throttling limits which in reality
made no difference to outlook performance.

[KB18141] - Microsoft Services are unavailable after upgrade to
Junos 10.1 and later versions

MS- RPC ALG is available and enabled by default on SRX-Branch and
J-Series platforms running Junos 10.0 and later. However beginning with Junos 10.1, the
MS-RPC ALG was added for SRX-HE platforms and enabled by default. This may
cause issues with Microsoft traffic such as Exchange and Active Directory
(refer to PSN-2010-08-912

Overview: Get-LogonStatistics assisted this issue as I could
directly compare between the client and server and confirmed that the CAS server
thought it was still holding an active connections when in fact it had been
closed by the firewall.

Biography

For the past number of years I have been busy in the Microsoft Exchange, Lync and Office 365 Space. We have been able to complete some really awesome and unique things which might be of some value to the Exchange and Lync Community.
Anyway that's the hope....